Fluid-pressure hammer



M. O FARRELL April 16, 1929.

FLUID PRESSURE HAMMER Filled July 27. 192s x AV www M, N E

lifatented pr. 16, 1529.

UNITEDSTATES PATENT OFFICE.

MATTHEW OFARRELL, OF DETROIT, MCHIGAN, ASSIGNOR T CHICAGO PNEUMATIC TOOL COMFANY, OF 'NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

FLUID-PREssURE HAMMER.

Application ined July 27, 192e. serial No. 125,153.

This invention relates to percussive tools operated by fluid pressure. It concerns the valve and piston action of such tools generally with particular reference to that type which utilizes a piston with an interior chamber into which extends a motive fluid inlet plug. Y

Among the objects of the invention are to provide a simple compact form of percussive tool which is fast and powerful, to effect exact coordination of pistonfand valve movement, to increase the force of the blow in tools of the specilietype described, and in general to improve prior devices. in the interests of more efficient and satisfactory service.

In order to illustrate the invention one concrete embodiment thereof is shown in the accompanying drawings, in which;

Fig. 1 is a longitudinal vertical sectional view of a hammer embodying` the invention; and

lFig. 2 is a sectional view similar to 1 showing the parts in a differentposition.

The embodiment of the invention chosen for the. purpose of illustration comprises a pneumatic hammerhaving a cylinder 3 providing a piston chamber 4lin which reciprocates a hammer piston 5 arranged 'to impart blows to a working .tool such as a drill steel 6, supported in a front head 7, either directly or through an anvil block 8 mounted in a guide member 9 bet-Ween cylinder 3 and front head 7. Piston 5 is hell-owed out rearwardly as indicated to provide an interior chamber 5'with a reduced opening 5". A, plug member/10,V mounted in the cylinder so as to proliectcentrally and axially into piston chamlb'er el cooperates With opening 5b in the pistonan'd serves as an inlet member for motive Afluid to the chamber 5aM b-y rea-son of an axial bore 11 through plug` 10 which communicates with the motive-fluid inlet passage 12, which is a branch of suppl) passage 13 back head Y14: of the drill, which supply passage mav7 be controlled by the-manually operated throttle valve 15. Another branch supplyv passage 16 loads from the supply 13 to an automatic valve 17 of the spool type having end heads 17a and 17b of equal diameter and reciprocable in valve chamber 18. End head 17?L controls passage 19 opening into the rearend of pistonchamber which isenlarged for a short dist-ance by an annular groove` 20. End head 17 controls passage 21 opening through a port 21a in the frontend of the piston chamber 4.

A passage 22 leads from enlarged end 2() of pistonchamber l to the pressure area presented by end head 17", yand a live air passage 23 of smaller size extends from supply passage 13 to the pressure area presented by opposite end head 17 a. A vent passage 23a extends from passage 23 and opens into piston chamber 4 so as to be under control of piston 5. In certain positions of the piston this vent passage registers with a groove 24 in the exterior of the piston. vCylinder 3 has main exhaust ports 25 and 2G for the piston chamber under control of piston 5.

The cycle of the voperation of the hammer is as follows Assuming throttle valve to be opened as indicated and starting with the parts in the position shown in Fig. 1, motive fluid from supply 13 passes through the bore 11 of plug 10 continuously into chamber 5 and is operative against the forwardly directed pressure area 5c provided by the end Since the reduced bore of the piston registers with the reduced neck 10?* of plug 10, motive fluid from chamber 5a passes into the enlarged chamber 20 at the rear end of piston chamber Lland is operable against the other forwardly directed area 5d provided by the rear end ofthe piston for a limited period or until the piston has moved forwardly Yto a slight extent. Meantime the motive fluid passing to chamber is effective through passage 22 against end head 17 b" of valve 17 to move it to the position shown so as toadmit motive fluid from branch 16 around the central reduced wall of this chamber. 5b

portion of the valve also Ito the rear end of the piston chamber through passage 19. The forwardend of the piston chamber is open to exhaust through port 25. As the piston moves forward to strike its blow the valve exhaust passage 23a no longer communicates With the groove 24 but is sealed by the piston `so that motive fluid entering through the live air passage 23 builds up vagainst end head 17 and becomes effective as soon as the rear end of the piston chamber is open to exhaust through uncovering of vent 2G by the piston. Valve 17- then shifts to the position shown in Fig. 2 cutting off passage 19 and establishing communication between passages 16 and 21 whereupon motive fluid enters the front of the piston chamberthrough port 21a to be effective against return area of the piston to drive the piston on its rearward stroke against the constant pressure of forwardly directed area 5"'. As the piston approaches the rear of the piston chamber it establishes communication between vent passage Q3 oil.

the valve and main exhaust port 26 through its groove 24 but valve 17 does not move rearwardly until the piston reaches the point where motive fluid fromconstant pressure chamber ,5a passes around neck l0 of plug l0 into the rear end of the piston chamber to augment the pressure of the air ltrapped therein and iseffective through passage 22 to shift the valve. T his completes the cycle.

'From the above it will be apparent that the ypresent invention relates to a fluid pressure hammer having a piston with two forwardly directing pressure areas and one return area, that one forward area is continuously subjected to pressure while the second forwardly directed area is intermittently subjected to pressure for a limited period, that a valve is arranged also to admit mot-ive fluid to this second forwardly directed area from an independent source and to continue the admission after the piston controlled means is closed, that Athe valve is thrown to admitting position by the motive fluid admitted by the piston control means, that the valve also controls the motive fluid supply to the return area of thepiston, that the forward may continuously active pressure area of the piston is provided by an interior chamber to which motive fluid is continuously admitted by avnecked plug inlet-and that the hammer comprises few parts of substantial size which be cheaply manufactured and assembled.'

1While a preferred form of the invention has been herein shown and described, it is to be understood that the invention is not limited to the specific details thereof but covers all changes, modifications, and adaptations within the scope of the appended claims.

I claim as my invention: l -1. A fluid pressure tool comprising a cylinder providing a piston chamber, a piston reeiprocable therein having two pressure areas :for ;l.riving it in one direction and a single area vfor returning it, means subjecting one of said first named areas continuously to motive fluid, piston controlled means for admitting motivek fluid to the second of said first named areas at the beginning of the stroke of the piston in one direction, and a valve controlling a second motive fluid supply rto said second of said first named areas and ther 'motive fluid supply vto said return area. y y

l 2L A fluid pressure tool comprising a cyl- `inder'providing a piston chamber, a piston reciproca-ble therein having two pressure areas for driving it in one direction and a single area for returning it, means subjecting one of said first named areas continuously to motive fluid, piston controlled -means for admitting motive fluid to lthe second of said first named areas at the beginning of the stroke of the piston in one direction, and a valvecontrolling a second motive lluid supply to said second of said firstpnamed areas and the motive .fl-uid supply to 'said return area, said valve being moved in one direction by 'he motive fluid admitted to the second of said first named areas by said piston controlled means. Y

A fluid pressure tool comprising a cylinder providing 'a piston chamber, a piston reciprocable therein having two pressure areas for driving it in one direction and single area for returning it, means subjecting one of said first named areas continuously to motive -fluid, piston controlled areas Afor admitting motive fluid to the second of said first named areas atrthe beginning of the stroke of .thepiston in one direction, and a valve controlling a second motive 'lluid supply to said second of said first namedl areas and the motive fluid supplyV to said return area, said valve being movable to the position Vto admit motive fluid to the second of said first named areas by the motive fluid admitted thereto by said piston controlled means and being movable to 'the position to admit motive fluid to the return area of said piston by abuilt-up pressure controlled by said piston.

l. A fluid pressure tool comprising a cylinder, a khammer piston reciprocable therein, said pis'tonhaving -a chamber therein providing a pressure area for driving it forwardly, a fixed member extending axially into said cylinder to admit motive fluid continuously to said chamber, said member having a reduced portion to permit motive fluid from 'said chamber to pass for a limited period to the rear end of said piston to be effective against the varea 4there presented, .an d an automatic valve controlled by said piston foradmitting motive fluid tov said last named area of the piston lduring and after said limitedV period, said valve being thrown to admit motive fluid yto said area by the motive fluid admitted thereto by said member and Ysaid piston. f i 5. A fluid pressure tool comprising acylinder, a hammer pistonreciprocable therein havingopposed'pressure areasat its ends and an interior pressure area, a plug member fixedly mounted in said cylinder and extending withinsaid piston continuously to supply motive fluid to said interior area, means permitting passage' of motive fluid from the interior of said piston to oneend area, and an automatic lvalve controlled by said piston for controlling the admissionofmotive fluid to both said Aend areas.

having opposed pressure areas at its ends and an interior pressure area, a plug member fixedly mounted in said cylinder and extending Within said piston continuously to supply motive fluid to said interior area, cooperating means on said piston and said member permitting access of motive fluid from the interior of said piston for a limited period to one end area of the piston, an d an automatic valve controlling a separate motive fluid supply to both said end areas of the piston.

7. A fluid pressure tool comprising a cylinder, a hammer piston reciprocable therein, having opposed pressure areas at its ends and an interior pressure area, a plug member fixedly mounted in said cylinder and extending Within said piston continuously to supply motive fluid to said interior area, said member having its exterior reduced at one point to permit motive fluid to pass from the inte'- rior of the piston to one end area thereof in one position of the piston, and an automatic valve controlling a separate motive fluid supply to both said end areas of the piston.

8. A fluid pressure tool comprising a cylin- V der, a hammer piston reciprocable therein,

having opposed pressure areas at its ends and an interior pressure area, a plug fixedly mounted in said cylinder and extending Within said piston continuously to supply motive fluid to said interior area, cooperating means on said piston and said member permitting access of motive fluid from the interior of said piston for a limited period to one end area of the piston, and an automatic valve controlling a separate motive fluid supply to both said end areas of the piston, said valve being moved in one direction on admission of motive fluid from the interior of the piston to said end area.

9. A fluid pressure tool comprising a cylinder, a hammer piston reciprocable therein, having opposed pressure areas at its ends and an interior pressure area, a plug member fixedly mounted in said cylinder and extending Within said piston continuously to supply motive fluid to said interior area, cooperating means on said piston and said member permitting access of' motive fluid from the interior of said piston for a limited period to one end area of the piston, and an automatic valve controlling a separate motive fluid supply to both said end areas of the piston, said valve being moved on admission of motive fluid from the interior of the piston to said end area to a position to admit additional motive fluid from said separate supply to said same area. Y

l0. A fluid pressure tool comprising a cylinder, a hammer piston reciprocable therein, said piston having a chamber therein providing a pressure area for driving it forwardly, a fixed member extending axially into said cylinder to admit motive fluid continuously to said chamber, said chamber having a reduced portion to permit motive fluid from said chamber to pass for a limited period to the rear end of said piston to be effective. against the area there presented, a spool valve having end heads of equal diameter operating in timed relation With the movements of the piston, said valve having a central reduced portion continuously supplied With motive fluid and said end heads controlling the distribution of the motive Huid to the opposed end areas of the piston in alternation, and means whereby the valve is moved to the position to admit motive fluid to the forwardly directed end area of the piston so as to supplement the limited admission of motive fluid thereto from said piston chamber.

Signed by me at Detroit, Mich., this 19th day of July, 1926.

MATTHEW OFARRELL. 

